U.S. patent number 7,883,761 [Application Number 12/509,107] was granted by the patent office on 2011-02-08 for multiple layer polymer interlayers having an embossed surface.
This patent grant is currently assigned to Solutia Inc.. Invention is credited to David Paul Bourcier, John Joseph D'Errico, Jean-Pierre Etienne, Gary Matis, Vincent James Yacovone.
United States Patent |
7,883,761 |
Bourcier , et al. |
February 8, 2011 |
**Please see images for:
( Certificate of Correction ) ** |
Multiple layer polymer interlayers having an embossed surface
Abstract
The present invention provides multiple layer interlayers having
a relatively soft inner layer and relatively stiff outer layers
that can be laminated without unacceptable optical distortion and
used in various multiple layer glass panel type applications.
Multiple layer interlayers of the present invention have surface
topography that is formed by embossing the exposed surface of the
interlayer, or individual layers of the multiple layer interlayer,
after formation of the interlayer or layers. The embossing process
is carried out under temperature conditions that prevent the
transfer of the embossing to inner layers of the interlayer. By
precisely controlling the embossing of the interlayer, lamination
of the interlayer with a rigid substrate does not lead to
unacceptable optical distortion caused by the transfer of the
surface topography through outer, stiffer layers into softer,
internal layers of the interlayer.
Inventors: |
Bourcier; David Paul (Ludlow,
MA), D'Errico; John Joseph (Glastonbury, CT), Etienne;
Jean-Pierre (Rhode St Genese, BE), Matis; Gary
(Wilbraham, MA), Yacovone; Vincent James (Springfield,
MA) |
Assignee: |
Solutia Inc. (St. Louis,
MO)
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Family
ID: |
39628900 |
Appl.
No.: |
12/509,107 |
Filed: |
July 24, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090286046 A1 |
Nov 19, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11741765 |
Apr 29, 2007 |
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Current U.S.
Class: |
428/141; 428/525;
428/436; 428/437 |
Current CPC
Class: |
B32B
17/10761 (20130101); B32B 38/06 (20130101); B32B
17/10587 (20130101); B32B 37/153 (20130101); Y10T
428/3163 (20150401); Y10T 428/31627 (20150401); Y10T
428/254 (20150115); Y10T 428/24355 (20150115); Y10T
428/24405 (20150115); Y10T 428/24612 (20150115); B32B
2329/06 (20130101); Y10T 428/31946 (20150401); B32B
2250/03 (20130101) |
Current International
Class: |
B32B
3/30 (20060101); B32B 27/42 (20060101) |
Field of
Search: |
;428/141,436,437,525 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 710 545 |
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May 1996 |
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EP |
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06-115982 |
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Apr 1994 |
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JP |
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09-040444 |
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Feb 1997 |
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JP |
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10-045438 |
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Feb 1998 |
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JP |
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2000-256043 |
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Sep 2000 |
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JP |
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2004-067414 |
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Mar 2004 |
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JP |
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2004-083360 |
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Mar 2004 |
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JP |
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2004-168646 |
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Jun 2004 |
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JP |
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95/05283 |
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Feb 1995 |
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WO |
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95/19885 |
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Jul 1995 |
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WO |
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WO2004/018197 |
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Mar 2004 |
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WO |
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WO2005/005123 |
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Jan 2005 |
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WO |
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Other References
Tokyo Seimitsu C., Ltd., "Measuring Machine of Surface Roughness
Shape SURFCOM Series Description on Parameters", First Edition
published Apr. 1, 1999, Seventh Edttion published Jul. 23, 2004,
First page, p. 6-1 and last page, with English translation. Apr. 1,
1999. cited by examiner.
|
Primary Examiner: Nakarani; D. S
Attorney, Agent or Firm: Lewis, Rice & Fingersh,
L.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to and is a continuation of
copending U.S. application Ser. No. 11/741,765 filed on Apr. 29,
2007, which is hereby incorporated by reference in its entirety.
Claims
We claim:
1. A polymer interlayer comprising: a first polymer layer
comprising a plasticized thermoplastic polymer; a second polymer
layer comprising a plasticized thermoplastic polymer; and, a third
polymer layer comprising a plasticized thermoplastic polymer;
wherein said second polymer layer is disposed between said first
polymer layer and said third polymer layer; wherein said first
polymer layer has a tensile break stress that is at least 15
kilograms per square centimeter greater than the tensile break
stress of said second polymer layer; wherein said third polymer
layer has a tensile break stress that is at least 15 kilograms per
square centimeter greater than the tensile break stress of said
second polymer layer; wherein the surface of said first polymer
layer opposite said second polymer layer has an embossed Rz value
of 50 to 90 microns; and, wherein said first polymer layer has a
thickness 0.05 to 0.71 millimeters.
2. The interlayer of claim 1, wherein said surface of said first
polymer layer opposite said second polymer layer has an embossed
Rsm value of less than 700 microns.
3. The interlayer of claim 1, wherein the surface of said third
polymer layer opposite said second polymer layer has an embossed Rz
value of 50 to 90 microns, an embossed Rsm value of less than 700
microns, and a permanence of less than 95%.
4. The interlayer of claim 1, wherein said first polymer layer,
said second polymer layer, and said third polymer layer each
comprise poly(vinyl butyral).
5. The interlayer of claim 1, wherein the surface of said first
polymer layer opposite said second polymer layer has an embossed Rz
value of 50 to 70 microns.
6. A polymer interlayer comprising: a first polymer layer
comprising a plasticized thermoplastic polymer; a second polymer
layer comprising a plasticized thermoplastic polymer; and, a third
polymer layer comprising a plasticized thermoplastic polymer;
wherein said second polymer layer is disposed between said first
polymer layer and said third polymer layer; wherein said first
polymer layer has a tensile break stress that is at least 15
kilograms per square centimeter greater than the tensile break
stress of said second polymer layer; wherein said third polymer
layer has a tensile break stress that is at least 15 kilograms per
square centimeter greater than the tensile break stress of said
second polymer layer; wherein the surface of said first polymer
layer opposite said second polymer layer has a permanence value of
less than 95%; and wherein said surface of said first polymer layer
opposite said second polymer layer has an Rz value of 50 to 90
microns and a thickness of 0.05 to 0.71 millimeters.
7. A polymer interlayer comprising: a first polymer layer
comprising a plasticized thermoplastic polymer; a second polymer
layer comprising a plasticized thermoplastic polymer; and a third
polymer layer comprising a plasticized thermoplastic polymer;
wherein said second polymer layer is disposed between said first
polymer layer and said third polymer layer; wherein said first
polymer layer has a residual hydroxyl content of less than 25
weight percent; wherein said second polymer layer has a residual
hydroxyl content of less than 23 weight percent; wherein the
surface of said first polymer layer opposite said second polymer
layer has an embossed Rsm value of less than 700 microns; and
wherein said surface of said first polymer layer opposite said
second polymer layer has an Rz value of 50 to 90 microns and a
thickness of 0.05 to 0.71 millimeters.
Description
FIELD OF THE INVENTION
The present invention is in the field of polymer interlayers and
multiple layer glass panels comprising polymer interlayers, and,
more specifically, the present invention is in the field of polymer
interlayers comprising multiple thermoplastic polymer layers.
BACKGROUND
Poly(vinyl butyral) (PVB) is commonly used in the manufacture of
polymer layers that can be used as interlayers in
light-transmitting laminates such as safety glass or polymeric
laminates. Safety glass often refers to a transparent laminate
comprising a poly(vinyl butyral) layer disposed between two sheets
of glass. Safety glass often is used to provide a transparent
barrier in architectural and automotive openings. Its main function
is to absorb energy, such as that caused by a blow from an object,
without allowing penetration through the opening or the dispersion
of shards of glass, thus minimizing damage or injury to the objects
or persons within an enclosed area. Safety glass also can be used
to provide other beneficial effects, such as to attenuate acoustic
noise, reduce UV and/or IR light transmission, and/or enhance the
appearance and aesthetic appeal of window openings.
The thermoplastic polymer found in safety glass can consist of a
single layer of a thermoplastic polymer, such as poly(vinyl
butyral), or multiple layers. Multiple layers are useful, for
example, in acoustic applications. Conventional attempts at such
acoustic dampening have included using thermoplastic polymers with
low glass transition temperatures. Other attempts have included
using two adjacent layers of thermoplastic polymer wherein the
layers have dissimilar characteristics (see, for example U.S. Pat.
Nos. 5,340,654 and 5,190,826, and U.S. Patent Application
2003/0139520 A1).
A particular problem encountered with multiple layer interlayers
arises at the lamination stage of processing. While single layer
interlayers have conventionally been embossed with rollers to
impart a texture that facilitates deairing, three layer interlayers
having a relatively soft inner layer between two relatively stiff
layers can develop optical distortion if embossing of the outer
surfaces of the interlayer is transferred to the inner, softer
layer. European application EP 0 710 545 A1 details this problem,
and cautions against embossing too deeply on the outer layers of a
three layer interlayer.
Further improved compositions and methods are needed to enhance the
production and optical characteristics of multiple layer glass
panels, and specifically multiple layer glass panels comprising
multiple layer interlayers.
SUMMARY OF THE INVENTION
The present invention provides multiple layer interlayers having a
relatively soft inner layer and relatively stiff outer layers that
can be laminated without unacceptable optical distortion and used
in various multiple layer glass panel type applications.
Multiple layer interlayers of the present invention have surface
topography that is formed by embossing the exposed surface of the
interlayer, or individual layers of the multiple layer interlayer,
after formation of the interlayer or layers. The embossing process
is carried out under temperature conditions that prevent the
transfer of the embossing to inner layers of the interlayer.
By precisely controlling the embossing of the interlayer,
lamination of the interlayer with a rigid substrate does not lead
to unacceptable optical distortion caused by the transfer of the
surface topography through outer, stiffer layers into softer,
internal layers of the interlayer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 represents a schematic cross sectional view of a multiple
manifold coextrusion device of the present invention.
DETAILED DESCRIPTION
The present invention is directed to multiple layer interlayers
that are useful in laminated glass applications in which a softer
inner polymer layer is disposed between and in contact with more
rigid outer layers, for example in applications in which sound
suppression is particularly desirable.
One type of multiple layer interlayer that utilizes softer inner
layers is multiple layer acoustic interlayers. As disclosed herein,
acoustic interlayers of the present invention comprise multiple
layers, with a preferred embodiment having a relatively soft layer
sandwiched between two relatively stiff layers. The resulting three
layer interlayer can generally be used in lamination processes
directly in place of conventional, single layer interlayers, with
little or no modification to the lamination process.
While the invention will be described herein throughout as
applicable to such acoustic interlayers, it will be understood by
those of skill in the art that the invention includes multiple
layer interlayers--for example three layer interlayers--having an
inner polymer layer that is softer than the outer layers between
which it is disposed, which includes non-acoustic multiple layer
interlayers.
According to the present invention, it has now been surprisingly
discovered that deairing and lamination of multiple layer
interlayers can be facilitated by embossing the outer surfaces of a
multiple layer interlayer without thereby also creating optical
distortion in the glazing panel in which the interlayer is used.
This result is accomplished by allowing the multiple layer
interlayer to cool after initial extrusion, for example after
coextrusion of a three polymer layer interlayer, and prior to
embossing. The interlayer, in various embodiments, is cooled below
90.degree. C., 80.degree. C., 70.degree. C., or 60.degree. C. In a
preferred embodiment, the interlayer is cooled below 60.degree.
C.
After cooling, in various embodiments of the present invention,
continuously unwound polymer in rolled form, or directly from the
die, is fed as a single layer to an embossing station having an
embossing roll pressing against a rubber-faced backup roll 10 to 60
centimeters (4'' to 24'') in diameter at any suitable speed, for
example at 305-915 centimeters per minute (10-30 feet per minute).
The shaping surface of the embossing roll can be engraved with any
desirable surface pattern. In one embodiment, for example, the
entire shaping surface of the embossing roll is engraved with a
sawtooth configuration. A sawtooth configuration is V-shaped in
vertical cross section with the sides of immediately adjacent
sawteeth at ninety degrees to each other. The sawteeth form
continuous helical ridges on the roll surface, which can be
oriented at 45 degrees with respect to the longitudinal roll axis.
The frequency of the ridges can be, for example, 127 to 508 per
centimeter, or 203 to 508 per centimeter (50 to 200 per inch or 80
to 200 per inch) as measured across the direction of the helix.
The face of the cooperating backup roll can be covered with a high
extensibility, temperature-resistant rubber capable of stretching
without fracturing. The surface of the embossing roll is regulated
to the desired temperature, for example, 121.degree. C. to
232.degree. C. (250.degree. F. to 450.degree. F.), 138.degree. C.
to 216.degree. C. (280.degree. F. to 420.degree. F.), or
149.degree. C. to 204.degree. C. (300.degree. F. to 400.degree. F.)
by the presence of an appropriate heating medium beneath the
embossing surface. A vacuum roll downstream of the nip formed by
the embossing and backup rolls can be used to pull the embossed
layer from the embossing roll surface. The layer, after passing
through the nip, can be removed by the vacuum roll beyond the nip,
and then can be passed with high wrap (>135 degrees) over a
chilled cooling roll (below 4.44.degree. C. (40.degree. F.)) and
then wound into a roll. Alternatively, embossing two sides of an
interlayer can be accomplished by passing the interlayer through
the same embossing set up a second time, or through a similar,
second set up down line.
The interlayer, as described above, can be embossed by heating the
outside surfaces of the interlayer to any suitable temperature and
at any suitable speed that does not cause the transfer of the
embossing pattern into the soft layer/stiff layer interface.
Temperatures can be, for example, 121.degree. C. to 232.degree. C.
(250.degree. F. to 450.degree. F.), 138.degree. C. to 216.degree.
C. (280.degree. F. to 420.degree. F.), or 149.degree. C. to
204.degree. C. (300.degree. F. to 400.degree. F.), and those
temperatures can be attained, for example, by processing the
interlayer through embossed rollers heated to the desired
temperature and having the desired embossing pattern.
Without being bound to theory, it is believed that, by precisely
controlling the temperature of the interlayer to maintain a low
inner temperature while the outside surfaces are heated
sufficiently to allow for embossing and controlling the permanence
of the embossed surface, the embossed pattern is effectively kept
from pushing through the outer stiffer layers and into the
interface between the outer layer and the inner layer at the time
of embossing and then later, at the time of lamination. It is the
distortion of that interface through embossing and/or laminating
that is believed to cause optical distortion in laminates, as has
been reported in some prior art (see, for example, EP 0 710 545
A1). Indeed, where that prior art warns against embossing too
deeply, multiple layer interlayers of the present invention are not
so restricted and, as will be described in detail below, can be
embossed well beyond the limits proposed in the prior art.
Embossing is a method of providing a roughened deairing surface to
a polymer interlayer or layer (see, for example, U.S. Pat. Nos.
5,425,977 and 6,077,374). Conventional techniques for embossing a
polymer layer include passing the layer through a nip between two
rotating rolls, one or both of which are embossing rolls having
indentations formed in its surface which are complementarily-shaped
negatives of the desired embossment pattern (see, for example, U.S.
Pat. Nos. 4,671,913; 2,904,844; 2,909,810; 3,994,654; 4,575,540;
5,151,234 and European Application No. 0185,863). Embossing
patterns can be regular or random, depending on the
application.
One or both surfaces of the outer polymer layers of the interlayer
are produced using embossing to produce a layer having the desired
"roughness", or "R.sub.Z", "pitch", or R.sub.SM, and permanence.
R.sub.Z is a measure of the surface topography of a polymer layer
and is an indication of divergence of the surface from a plane.
R.sub.SM is a measure of the distance between peaks in the
topography of the surface of a polymer layer. "Permanence" is a
measure of the tendency of the surface of the embossed interlayer
to resist the memory inherent in the layer, which results in a
tendency of the surface to return to the surface topography that
existed prior to embossing. The three measurements will be
described in detail, below.
In various embodiments of the present invention, a multiple layer
interlayer having a softer inner polymer layer is produced using
the embossing techniques taught herein in which one or both of the
outer surfaces of the interlayer have an R.sub.Z value of 50 to 90,
60 to 90, or 60 to 80. The two outer surfaces can have the same
R.sub.Z value or a different value. In other embodiments, only one
of the two outer surfaces has the designated R.sub.Z value. In yet
other embodiments, either one or both of the outer layers of an
interlayer have the designated R.sub.Z value on the inner surface,
which is disposed in contact with an inner, relatively soft layer,
which is found, for example, in non-coextrusion embodiments in
which multiple individual layers are laminated together to form a
multiple layer interlayer.
In various embodiments of the present invention, the outer surfaces
of an interlayer of the present invention have an R.sub.SM value of
less than 700, 650, or 600. In further embodiments, only one outer
surface has the designated R.sub.SM value. In yet other
embodiments, one or both of the inner surfaces of the outer layers
of an interlayer have the designated R.sub.SM value. The R.sub.SM
values given can be combined with the R.sub.Z values given in any
suitable combination to produce the desired surface
characteristics.
Multiple layer interlayers of the present invention, in various
embodiments, have a "permanence value", which will be described in
detail below, of less than 95%, less than 90%, less than 80%, less
than 70%, or less than 60%, and these permanence values, again, can
be combined with any of the given R.sub.SM values and R.sub.Z
values in any suitable combination to produce the desired surface
characteristics. In other embodiments, permanence values of one or
both outer surfaces are 40% to 95% or 50% to 90%.
Examples of preferred combinations of the three surface
characteristics for one or both surfaces of the multiple layer
interlayers of the present invention include, without limitation,
the following combinations, which are arranged in the order
R.sub.Z///R.sub.SM///permanence and are separated by semicolons,
and where R.sub.Z and R.sub.SM are given in microns and permanence
is given as a percentage: 50 to 90///any///less than 95; 50 to
90///any///less than 90; 50 to 90///any///40 to 95; 50 to 90///less
than 700///less than 95; 50 to 90///less than 700///less than 90;
50 to 90///less than 700///40 to 95; 60 to 80///any///less than 95;
60 to 80///any///less than 90; 60 to 80///any///40 to 95; 60 to
80///less than 700///less than 95; 60 to 80///less than 700///less
than 90; and 60 to 80///less than 700///40 to 95.
The resulting interlayer, with the specified R.sub.Z and/or
R.sub.SM and/or permanence value can be readily laminated between
two glazing layers such as glass. The R.sub.Z and R.sub.SM values
given above, which are imparted by embossing and which are present
on at least one, and preferably both outer surfaces of the outer
layers of a multiple layer interlayer, result in outer surfaces
that can be readily deaired after they are placed in contact with
glass layers and laminated, for example using a vacuum bag deairing
process.
As used herein, having an "embossed X value", where "X" is R.sub.Z
or R.sub.SM, means that surface qualities measured by R.sub.Z and
R.sub.SM have been produced through embossing after the extrusion
and cooling, and it is the embossed surface that is being
measured.
Some embodiments of multiple layer interlayers of the present
invention that function to reduce sound transmission through a
glass panel include those known in the art, for example, and not
limited to, those disclosed in U.S. Pat. No. 5,190,826, which
teaches the use of acetals of differing carbon length, Japanese
Patent Application 3124441A and U.S. Patent Application
2003/0139520 A1, which teach the use of differing polymerization
degree, and Japanese Patent 3,377,848 and U.S. Pat. No. 5,340,654,
which teach the use of residual acetate levels of at least 5 mole %
in one of two adjacent layers as a compositional difference.
In a preferred embodiment, superior sound suppression
characteristics can be imparted to multiple layer glass panels by
incorporating a multiple layer interlayer into the panels, where
the interlayer comprises two polymer layers having different
plasticizer concentrations.
By formulating polymer layers as described above, sound
transmission through multiple layer glass panels can be reduced by,
for example, more than 2 decibels in the frequency or frequency
region of interest. Further, because embodiments having three
polymer layer layers can be formulated to be easily handled and
used as a direct replacement for conventional interlayers in
conventional processes, interlayers of the present invention will
be usable in many applications without requiring any modification
to the manufacturing method used in the applications. For example,
automotive windshield applications can involve the use of a
conventional polymeric interlayer that can be replaced with an
interlayer of the present invention without altering the lamination
process used to form the finished windshield.
As used herein, an "interlayer" is any thermoplastic construct that
can be used in multiple layer glass applications, such as safety
glass in windshields and architectural windows, and a "multiple
layer" interlayer is any interlayer that is formed by combining,
usually through laminating processes or coextrusion, two or more
individual layers into a single interlayer.
In various embodiments of the present invention, a multiple layer
interlayer comprises two polymer layers disposed in contact with
each other, wherein each polymer layer comprises a thermoplastic
polymer, as detailed elsewhere herein. The thermoplastic polymer
can be the same or different in each layer.
In a preferred embodiment, as described below, a high plasticizer
content polymer layer is sandwiched between two low plasticizer
content layers to form a three layer interlayer. The composition of
the polymer layers is such that net migration of plasticizer from
one polymer layer to another is negligible or zero, thereby
maintaining the plasticizer differential.
As used herein, "plasticizer content" can be measured as parts per
hundred resin (phr) parts, on a weight per weight basis. For
example, if 30 grams of plasticizer is added to 100 grams of
polymer resin, then the plasticizer content of the resulting
plasticized polymer would be 30 phr. As used herein throughout,
when the plasticizer content of a polymer layer is given, the
plasticizer content of that particular layer is determined with
reference to the phr of the plasticizer in the melt that was used
to produce that particular layer.
For layer of unknown plasticizer content, the plasticizer content
can be determined via a wet chemical method in which an appropriate
solvent, or a mixture of solvents, is used to extract the
plasticizer out of the layer. By knowing the weight of the sample
and the weight of the extracted layer, the plasticizer content in
phr can be calculated. In the case of a multiple polymer layer
interlayer, one polymer layer can be physically separated from the
other before the plasticizer content in each of the polymer layers
is measured.
In various embodiments of the present invention, the plasticizer
content of the two polymer layers differ by at least 8 phr, 10 phr,
12 phr, 15 phr, 18 phr, 20 phr, or 25 phr. Each layer can have, for
example 30 to 100 phr, 40 to 90 phr, or 50 to 80 phr.
In various embodiments of the present invention, the residual
hydroxyl contents of the thermoplastic polymer components of the
polymer layers are different, which allows for the fabrication of
layers with stable plasticizer differences. As used herein,
residual hydroxyl content (as vinyl hydroxyl content or poly(vinyl
alcohol) (PVOH) content) refers to the amount of hydroxyl groups
remaining as side groups on the polymer chains after processing is
complete. For example, poly(vinyl butyral) can be manufactured by
hydrolyzing poly(vinyl acetate) to poly(vinyl alcohol), and then
reacting the poly(vinyl alcohol) with butyraldehyde to form
poly(vinyl butyral). In the process of hydrolyzing the poly(vinyl
acetate), typically not all of the acetate side groups are
converted to hydroxyl groups. Further, reaction with butyraldehyde
typically will not result in all hydroxyl groups being converted to
acetal groups. Consequently, in any finished poly(vinyl butyral),
there will typically be residual acetate groups (as vinyl acetate
groups) and residual hydroxyl groups (as vinyl hydroxyl groups) as
side groups on the polymer chain. As used herein, residual hydroxyl
content is measured on a weight percent basis per ASTM 1396.
In various embodiments of the present invention, the residual
hydroxyl content of the two adjacent polymer layers can differ by
at least 1.8%, 2.0%, 2.2%, 2.5%, 3.0%, 4.0%, 5.0%, 7.5%, or by at
least 10%. This difference is calculated by subtracting the
residual hydroxyl content of the layer with the lower residual
hydroxyl content from the residual hydroxyl content of the layer
with the greater residual hydroxyl content. For example, if a first
polymer layer has a residual hydroxyl content of 20 weight percent,
and a second polymer layer has a residual hydroxyl content of 17
weight percent, then the residual hydroxyl content of the two
layers differs by 3 weight percent.
For a given type of plasticizer, the compatibility of that
plasticizer in a poly(vinyl butyral) is largely determined by the
hydroxyl content. Typically, poly(vinyl butyral) with a greater
residual hydroxyl content will result in a reduced plasticizer
compatibility or capacity. Likewise, poly(vinyl butyral) with a
lower residual hydroxyl content will result in an increased
plasticizer compatibility or capacity. These properties can be used
to select the hydroxyl content of each poly(vinyl butyral) polymer
and formulate each of the polymer layers to allow for the proper
plasticizer loading and to stably maintain the difference in
plasticizer content between the polymer layers.
As is known in the art, residual hydroxyl content can be controlled
by controlling reaction times, reactant concentrations, and other
variables in the manufacturing process. In various embodiments, the
residual hydroxyl content of the two layers is as follows: first
layer less than 25% and second layer less than 23%; first layer
less than 23% and second layer less than 21%; first layer less than
21% and second layer less than 19%; first layer less than 20% and
second layer less than 17%; first layer less than 18% and second
layer less than 15%; first layer less than 15% and second layer
less than 12%. In any of these embodiments, any of the values given
in a previous paragraph for the difference in hydroxyl content
between the two layers can be used.
As used herein throughout, the relative terms "soft/softer" and
"stiff/stiffer" refer to the tensile break stress of the polymer
layer. As used herein, tensile break stress, or tensile strength,
of a polymer layer is defined and measured according to the method
described in JIS K6771, with a relatively "soft" polymer layer
having a lower tensile break stress value than a relatively "stiff"
polymer layer. In various embodiments of the present invention, two
polymer layers have a tensile break stress according to the
following, wherein the first polymer layer in the following list is
the polymer layer with the lower plasticizer content: first polymer
layer greater than 135 kilograms per square centimeter and second
polymer layer less than 120 kilograms per square centimeter; first
polymer layer greater than 150 kilograms per square centimeter and
second polymer layer less than 135 kilograms per square centimeter;
first polymer layer greater than 165 kilograms per square
centimeter and second polymer layer less than 150 kilograms per
square centimeter; or first polymer layer greater than 180
kilograms per square centimeter and second polymer layer less than
165 kilograms per square centimeter. A third polymer layer,
disposed in contact with the second polymer layer opposite the
first polymer layer so as to sandwich the second polymer layer
between the first and third polymer layers, can be added to any of
the above embodiments, with the third layer having the same or
different composition as the first polymer layer, and preferably
having the same composition as the first polymer layer.
While the tensile break stress values provided in the preceding
paragraph represent values that could be used for acoustic type
multiple layer interlayers, those of skill in the art will
recognize that the methods and interlayers of the present invention
are useful for any multiple layer interlayer having a relatively
soft inner layer and one or more relatively stiff outer layers.
Accordingly, in various embodiments of the present invention, one
or both outer layers have a tensile break stress that is an least
15 kilograms per square centimeter, 20 kilograms per square
centimeter, or 25 kilograms per square centimeter greater than the
tensile break stress of a softer inner layer.
As used herein, a conventional laminated glass is formed through
laminating a conventional interlayer, which is typically used today
for commercial laminated glass, wherein the conventional interlayer
has a tensile break stress of 200 kilograms per square centimeter
or higher. For the purpose of the present invention, conventional
laminated glass is referred to as a "reference laminate panel" or
"reference panel."
Improvement in acoustic insulation as used to characterize glass
laminates consisting of the interlayers of the present invention is
determined with reference to a reference laminate panel as
described in the previous paragraph. In typical laminates with two
outer layers of glass, the "combined glass thickness" is the sum of
the thickness of the two layers of glass; in more complex laminates
with three or more layers of glass, the combined glass thickness
would be the sum of the three or more layers of glass.
For purposes of the present invention a "coincident frequency"
means the frequency at which a panel exhibit a dip in sound
transmission loss due to "coincident effect". The coincident
frequency of the reference panel is typically in the range of 2,000
to 6,000 Hertz, and can be empirically determined from a monolithic
sheet of glass having a thickness equal to the combined glass
thickness of glass in the reference panel from the algorithm
##EQU00001##
where "d" is the total glass thickness in millimeters and "f.sub.c"
is in Hertz.
For purposes of this invention, improvement in acoustic performance
can be measured by an increase in sound transmission loss at the
coincident frequency (reference frequency) of the reference
panel.
"Sound transmission loss" is determined for a laminate of the
present invention or conventional reference panel of fixed
dimensions with ASTM E90 (95) at a fixed temperature of 20.degree.
C.
In various embodiments of the present invention, multiple layer
interlayers of the present invention, when laminated between two
panes of glass sheet, reduce the transmission of sound through the
laminated glass panel by at least 2 decibels (dB) relative to a
comparable reference panel having a single conventional interlayer
with a thickness comparable to that of the multiple layer
interlayer of the present invention.
In various embodiments of the present invention, interlayers of the
present invention, when laminated between two sheets of glass,
improve the sound transmission loss by at least 2 dB, more
preferably 4 dB, more preferably 6 dB or higher, and even more
preferably 8 dB or higher at the reference frequency relative to a
comparable reference panel.
Prior art attempts to produce interlayers comprising adjacent
polymer layers that reduce sound transmission through a multiple
layer glass panel have relied on various compositional permutations
between those layers. Examples include U.S. Pat. No. 5,190,826,
which teaches the use of acetals of differing carbon length, and
Japanese Patent Application 3124441A and U.S. Patent Application
2003/0139520 A1, which teach the use of differing polymerization
degree. Two other applications, Japanese Patent 3,377,848 and U.S.
Pat. No. 5,340,654, teach the use of residual acetate levels of at
least 5 mole % in one of two adjacent layers as a compositional
difference.
In various embodiments of the present invention, and distinctly
different from the approach used in those applications, two
adjacent polymer layers of the present invention have the differing
plasticizer content as described above, and each further can have a
residual acetate content of less than 5 mole %, less than 4 mole %,
less than 3 mole %, less than 2 mole %, or less than 1 mole %.
These residual acetate concentrations can be combined with the
residual hydroxyl contents given above, in any combination, to form
two polymer layers of the present invention having the described
differences in plasticizer content and residual hydroxyl content
while having little to no residual acetate content. Further
embodiments of multiple layer interlayers of the present invention
include interlayers having more than two polymer layers, wherein
one or more of the additional polymer layers has a residual acetate
content of less than 5 mole %, less than 4 mole %, less than 3 mole
%, less than 2 mole %, or less than 1 mole %.
Further embodiments of the present invention, which are the
preferred embodiments, include any of the foregoing embodiments
further comprising a third polymer layer that is disposed in
contact with the softer polymer layer, for example, the one having
the higher plasticizer content. Addition of this third polymer
layer results in a three layer construct that has the following
structure: First polymer layer that is relatively stiff//Second
polymer layer that is relatively soft//Third polymer layer. This
third polymer layer can have the same composition as the first
polymer layer, as it does in preferred embodiments, or it can be
different. While the preferred embodiments of the present invention
have a soft inner layer disposed between an in contact with two
stiffer outer layers, it will be understood by those of skill in
the art that the methods of the present invention can also be
applied to two layer interlayers and interlayers having more than
three layers. For example, a variation within the scope of the
present invention would be a five layer interlayer having two
stiffer outer layers and three inner softer layers.
In various embodiments, the third polymer layer has the same
composition as the first polymer layer, which provides a three
layer interlayer that has a relatively difficult to handle polymer
layer disposed between two relatively easy to handle layers,
resulting in a multiple layer interlayer that is relatively easy to
handle and which can be incorporated directly into existing
processes that previously used a single polymer layer having the
composition of the outer two polymer layers of the interlayer of
the present invention, or a composition that results in similar
processing characteristics (for example, blocking tendency).
In other embodiments utilizing three polymer layers in a single
interlayer, the third polymer layer has a different composition
than the first polymer layer, and the differences in composition
between the third polymer layer and the second polymer layer can be
any of the differences given above for the differences between the
first polymer layer and the second polymer layer. For example, one
exemplary embodiment would be: first polymer layer with a residual
hydroxyl content of 20%//second polymer layer with a residual
hydroxyl content of 16%//third polymer layer with a residual
hydroxyl content of 18%. It will be noted that, in this example,
the third polymer layer differs from the second polymer layer at
least in that it has a residual hydroxyl content that is 2% greater
than the hydroxyl content of the second polymer layer. Of course,
any of the other differences noted herein throughout can singly or
in combination distinguish the third polymer layer from the second
polymer layer.
Other conventional layers, as are known in the art, can be
incorporated into the interlayers of the present invention. For
example, polymer films (described in detail elsewhere herein) such
as polyesters like poly(ethylene terephthalate) having a metallized
layer, an infrared reflecting stack, or other performance layer
deposited thereon, can be included between any two polymer layers
of the present invention, where appropriate. For example, in a two
layer embodiment, an interlayer can be fabricated with the
following layout: polymer layer with relatively high plasticizer
content//polyester film having a performance layer//polymer layer
with relatively low plasticizer content. In general, additional
layers of thermoplastics, such as poly(vinyl butyral), polyester
films, primer layers, and hardcoat layers can be added to the
multiple layer interlayers of the present invention according to
the desired result and the particular application.
The preferred method of producing interlayers of the present
invention is through the simultaneous coextrusion of multiple, for
example three, polymer layers. For the purposes of the present
invention, coextrusion of multiple melts results in multiple
polymer layers being formed together as one interlayer.
Multiple layer interlayers of the present invention are preferably
coextruded using a multiple manifold coextrusion device such as the
one shown in FIG. 1. As shown in schematic cross sectional view
generally at 10, an extrusion device has a first die manifold 12 a
second die manifold 14, and a third die manifold 16. The device
shown in FIG. 1 operates by simultaneously extruding polymer melts
from each manifold (12, 14, 16) toward the extrusion opening 20,
where the multiple layer interlayer is extruded as a composite of
three individual polymer layers. Layer thickness can be varied by
adjusting the distance between the die lips at the extrusion
opening 20.
As used herein, a "polymer layer" includes layers that are produced
individually and layers that are coextruded. For example, an
interlayer that is produced by coextruding three melts will have
three individual "polymer layers" just as will an interlayer that
is produced by laminating three individually produced polymer
layers into a single interlayer.
In addition to the interlayers provided herein, the present
invention also provides methods of reducing the level of sound
through an opening, comprising the step of disposing in the opening
a multiple layer glass panel comprising any of the interlayers of
the present invention.
The present invention also includes methods of manufacturing a
multiple layer glazing, comprising laminating any of the
interlayers of the present invention between two rigid, transparent
panels, as are known in the art, such as glass or acrylic
layers.
The present invention also includes multiple layer glass panels,
such as windshields and architectural windows, comprising a
multiple layer interlayer of the present invention.
Also included are multiple layer glazing panels having plastics,
such as acrylics, or other suitable materials in place of the glass
panels.
The present invention also includes a method of making a polymer
interlayer having an internal layer with a relatively low tensile
break stress compared to the outside layers by forming a first
polymer melt, a second polymer melt, and a third polymer melt, and
optionally a fourth or more polymer melts; and, coextruding said
first polymer melt, said second polymer melt, and said third
polymer to form an interlayer, and, optionally, said fourth or more
polymer melts, cooling the interlayer to a suitable temperature, as
described elsewhere herein, heating a surface of the interlayer to
a suitable temperature, as described elsewhere herein, and,
embossing said surface of said interlayer to an R.sub.Z of 20 to
90, or 20-70.
For these embodiments, R.sub.SM and the permanence value can be any
as given elsewhere herein. Examples of preferred combinations of
the three surface characteristics for one or both surfaces of the
multiple layer interlayers of the present invention include,
without limitation, the following combinations, which are arranged
in the order R.sub.Z///R.sub.SM///permanence and are separated by
semicolons, and where R.sub.Z and R.sub.SM are given in microns and
permanence is given as a percentage: 20 to 90///any///less than 95;
20 to 90///any///less than 90; 20 to 90///any///40 to 95; 20 to
90///less than 700///less than 95; 20 to 90///less than 700///less
than 90; 20 to 90///less than 700///40 to 95; 20-70///any///less
than 95; 20-70///any///less than 90; 20-70///any///40 to 95;
20-70///less than 700///less than 95; 20-70///less than 700///less
than 90; and 20-70///less than 700///40 to 95.
Polymer Film
As used herein, a "polymer film" means a relatively thin and rigid
polymer layer that functions as a performance enhancing layer.
Polymer films differ from polymer layers, as used herein, in that
polymer films do not themselves provide the necessary penetration
resistance and glass retention properties to a multiple layer
glazing structure, but rather provide performance improvements,
such as infrared absorption character. Poly(ethylene terephthalate)
is most commonly used as a polymer film.
In various embodiments, the polymer film layer has a thickness of
0.013 mm to 0.20 mm, preferably 0.025 mm to 0.1 mm, or 0.04 to 0.06
mm. The polymer film layer can optionally be surface treated or
coated to improve one or more properties, such as adhesion or
infrared radiation reflection. These functional performance layers
include, for example, a multi-layer stack for reflecting infra-red
solar radiation and transmitting visible light when exposed to
sunlight. This multi-layer stack is known in the art (see, for
example, WO 88/01230 and U.S. Pat. No. 4,799,745) and can comprise,
for example, one or more Angstroms-thick metal layers and one or
more (for example two) sequentially deposited, optically
cooperating dielectric layers. As is also known, (see, for example,
U.S. Pat. Nos. 4,017,661 and 4,786,783), the metal layer(s) may
optionally be electrically resistance heated for defrosting or
defogging of any associated glass layers.
An additional type of polymer film that can be used with the
present invention, which is described in U.S. Pat. No. 6,797,396,
comprises a multitude of nonmetallic layers that function to
reflect infrared radiation without creating interference that can
be caused by metallic layers.
The polymer film layer, in some embodiments, is optically
transparent (i.e. objects adjacent one side of the layer can be
comfortably seen by the eye of a particular observer looking
through the layer from the other side), and usually has a greater,
in some embodiments significantly greater, tensile modulus
regardless of composition than that of any adjacent polymer layer.
In various embodiments, the polymer film layer comprises a
thermoplastic material. Among thermoplastic materials having
suitable properties are nylons, polyurethanes, acrylics,
polycarbonates, polyolefins such as polypropylene, cellulose
acetates and triacetates, vinyl chloride polymers and copolymers
and the like. In various embodiments, the polymer film layer
comprises materials such as re-stretched thermoplastic films having
the noted properties, which include polyesters, for example
poly(ethylene terephthalate) and poly(ethylene terephthalate)
glycol (PETG). In various embodiments, poly(ethylene terephthalate)
is used, and, in various embodiments, the poly(ethylene
terephthalate) has been biaxially stretched to improve strength,
and has been heat stabilized to provide low shrinkage
characteristics when subjected to elevated temperatures (e.g. less
than 2% shrinkage in both directions after 30 minutes at
150.degree. C.).
Various coating and surface treatment techniques for poly(ethylene
terephthalate) film that can be used with the present invention are
disclosed in published European Application No. 0157030. Polymer
films of the present invention can also include a hardcoat and/or
and antifog layer, as are known in the art.
Polymer Layer
As used herein, a "polymer layer" means any thermoplastic polymer
composition formed by any suitable method into a thin layer that is
suitable alone, or in stacks of more than one layer, for use as an
interlayer that provides adequate penetration resistance and glass
retention properties to laminated glazing panels. Plasticized
poly(vinyl butyral) is most commonly used to form polymer
layers.
The polymer layer can comprise any suitable polymer, and, in a
preferred embodiment, the polymer layer comprises poly(vinyl
butyral). In any of the embodiments of the present invention given
herein that comprise poly(vinyl butyral) as the polymeric component
of the polymer layer, another embodiment is included in which the
polymer component consists of or consists essentially of poly(vinyl
butyral). In these embodiments, any of the variations in additives
disclosed herein can be used with the polymer layer having a
polymer consisting of or consisting essentially of poly(vinyl
butyral).
In one embodiment, the polymer layer comprises a polymer based on
partially acetalized poly(vinyl alcohol)s. In another embodiment,
the polymer layer comprises a polymer selected from the group
consisting of poly(vinyl butyral), polyurethane, polyvinyl
chloride, poly(ethylene vinyl acetate), combinations thereof, and
the like. In other embodiments, the polymer layer comprises
plasticized poly(vinyl butyral). In further embodiments the polymer
layer comprises poly(vinyl butyral) and one or more other polymers.
Other polymers having a proper plasticizing capacity can also be
used. In any of the sections herein in which preferred ranges,
values, and/or methods are given specifically for poly(vinyl
butyral) (for example, and without limitation, for plasticizers,
component percentages, thicknesses, and characteristic-enhancing
additives), those ranges also apply, where applicable, to the other
polymers and polymer blends disclosed herein as useful as
components in polymer layers.
For embodiments comprising poly(vinyl butyral), the poly(vinyl
butyral) can be produced by known acetalization processes that
involve reacting poly(vinyl alcohol) with butyraldehyde in the
presence of an acid catalyst, followed by neutralization of the
catalyst, separation, stabilization, and drying of the resin, with
the understanding that in various embodiments, residual hydroxyl
content will be controlled, as described elsewhere herein.
In various embodiments, the polymer layer comprises poly(vinyl
butyral) having a molecular weight greater than 30,000, 40,000,
50,000, 55,000, 60,000, 65,000, 70,000, 120,000, 250,000, or
350,000 grams per mole (g/mole or Daltons). Small quantities of a
dialdehyde or trialdehyde can also be added during the
acetalization step to increase molecular weight to greater than
350,000 Daltons (see, for example, U.S. Pat. Nos. 4,874,814;
4,814,529; and 4,654,179). As used herein, the term "molecular
weight" means the weight average molecular weight.
If additional, conventional polymer layers are used in addition to
any of the embodiments described above as having plasticizer
content differences, those additional, conventional polymer layers
can comprise 20 to 60, 25 to 60, 20 to 80, or 10 to 70 parts
plasticizer per one hundred parts of resin (phr). Of course other
quantities can be used as is appropriate for the particular
application. In some embodiments, the plasticizer has a hydrocarbon
segment of fewer than 20, fewer than 15, fewer than 12, or fewer
than 10 carbon atoms.
Any suitable plasticizers can be added to the polymer resins of the
present invention in order to form the polymer layers. Plasticizers
used in the polymer layers of the present invention can include
esters of a polybasic acid or a polyhydric alcohol, among others.
Suitable plasticizers include, for example, triethylene glycol
di-(2-ethylbutyrate), triethylene glycol di-(2-ethylhexanoate),
triethylene glycol diheptanoate, tetraethylene glycol diheptanoate,
dihexyl adipate, dioctyl adipate, hexyl cyclohexyladipate, mixtures
of heptyl and nonyl adipates, diisononyl adipate, heptylnonyl
adipate, dibutyl sebacate, polymeric plasticizers such as the
oil-modified sebacic alkyds, and mixtures of phosphates and
adipates such as disclosed in U.S. Pat. No. 3,841,890 and adipates
such as disclosed in U.S. Pat. No. 4,144,217, and mixtures and
combinations of the foregoing. Other plasticizers that can be used
are mixed adipates made from C.sub.4 to C.sub.9 alkyl alcohols and
cyclo C.sub.4 to C.sub.10 alcohols, as disclosed in U.S. Pat. No.
5,013,779, and C.sub.6 to C.sub.8 adipate esters, such as hexyl
adipate. In preferred embodiments, the plasticizer is triethylene
glycol di-(2-ethylhexanoate).
Adhesion control agents (ACAs) can also be included in the polymer
layers of the present invention to impart the desired adhesiveness.
These agents can be incorporated into the outer layers in a three
polymer layer embodiment, for example. Any of the ACAs disclosed in
U.S. Pat. No. 5,728,472 can be used. Additionally, residual sodium
acetate and/or potassium acetate can be adjusted by varying the
amount of the associated hydroxide used in acid neutralization. In
various embodiments, polymer layers of the present invention
comprise, in addition to sodium acetate, magnesium bis(2-ethyl
butyrate) (chemical abstracts number 79992-76-0). The magnesium
salt can be included in an amount effective to control adhesion of
the polymer layer to glass.
Additives may be incorporated into the polymer layer to enhance its
performance in a final product. Such additives include, but are not
limited to, plasticizers, dyes, pigments, stabilizers (e.g.,
ultraviolet stabilizers), antioxidants, flame retardants, other IR
absorbers, anti-block agents, combinations of the foregoing
additives, and the like, as are known in the art.
Agents that selectively absorb light in the visible or near
infrared spectrum can be added to any of the appropriate polymer
layers. Agents that can be used include dyes and pigments such as
indium tin oxide, antimony tin oxide, or lanthanum hexaboride
(LaB.sub.6).
Any suitable method can be used to produce poly(vinyl butyral).
Details of suitable processes for making poly(vinyl butyral) are
known to those skilled in the art (see, for example, U.S. Pat. Nos.
2,282,057 and 2,282,026). In one embodiment, the solvent method
described in Vinyl Acetal Polymers, in Encyclopedia of Polymer
Science & Technology, 3.sup.rd edition, Volume 8, pages
381-399, by B. E. Wade (2003) can be used. In another embodiment,
the aqueous method described therein can be used. Poly(vinyl
butyral) is commercially available in various forms from, for
example, Solutia Inc., St. Louis, Mo. as Butvar.TM. resin.
As used herein, "resin" refers to the polymeric (for example
poly(vinyl butyral)) component that is removed from the mixture
that results from the acid catalysis and subsequent neutralization
of the polymeric precursors. Resin will generally have other
components in addition to the polymer, for example poly(vinyl
butyral), such as acetates, salts, and alcohols. As used herein,
"melt" refers to a mixture of resin with a plasticizer and,
optionally, other additives.
One exemplary method of forming a poly(vinyl butyral) layer
comprises extruding molten poly(vinyl butyral) comprising resin,
plasticizer, and additives and then forcing the melt through a
sheet die (for example, a die having an opening that is
substantially greater in one dimension than in a perpendicular
dimension). Another exemplary method of forming a poly(vinyl
butyral) layer comprises casting a melt from a die onto a roller,
solidifying the resin, and subsequently removing the solidified
resin as a sheet.
In various embodiments, a "prelaminate" interlayer is formed by
assembling the individual layers into a stack of layers, and then
subjecting the layers to sufficient heat and pressure to tack the
layers together, thereby forming the prelaminate. The prelaminate
can then be rolled or otherwise stored as desired until it is used
in a laminated glazing, at which point the prelaminate is placed
between two layers of glass and laminated to form the final
multiple layer glazing.
In various embodiments, the interlayers of the present invention
can have total thicknesses of 0.1 to 2.5 millimeters, 0.2 to 2.0
millimeters, 0.25 to 1.75 millimeters, and 0.3 to 1.5 millimeters
(mm). The individual polymer layers of a multiple layer interlayer
can have, for example, approximately equal thicknesses that, when
added together, result in the total thickness ranges given above.
Of course, in other embodiments, the thicknesses of the layers can
be different, and can still add to the total thicknesses given
above. For example, the outer layers can be 0.18 to 0.36
millimeters, and the inner layer can be 0.12 to 0.16 millimeters,
with a total thickness of 0.51 to 0.89 millimeters.
In various embodiments of the present invention, any of the layers,
and particularly the outer layers can have a thickness of 0.05 to
0.71 millimeters (2 to 28 mils), 0.05 to 0.64 millimeters (2 to 25
mils), or 0.05 to 0.51 millimeters (2 to 20 mils). These thickness
ranges can be combined with any of the values given elsewhere
herein for R.sub.Z, R.sub.SM, and permanence. In a preferred
embodiment, one or both of the outer layers of a multiple layer
interlayer has a thickness of 0.05 to 0.71 millimeters, 0.05 to
0.64 millimeters, or 0.05 to 0.51 millimeters and an R.sub.Z of 50
to 90, 60 to 90, or 60 to 80.
The parameters for the polymer layer described above apply as well
to any layer in a multiple layer construct of the present invention
that is a poly(vinyl butyral) type layer.
The following paragraphs describe various techniques that can be
used to improve and/or measure the characteristics of the polymer
layer.
To determine R.sub.Z and R.sub.SM, a 15 centimeter by 15 centimeter
test sample of plasticized polymer layer is placed on a vacuum
plate regulated by fluid at room temperature circulating through
it. A vacuum of 3.44 kPa (5 psi) is imposed to draw the sample
against the plate surface. A model S8P Perthometer with a PRK drive
unit and an RFHTB-250 tracing stylus (available from Mahr Gage Co.,
New York) is used to directly measure layer surface roughness of
each side of the test sample. Profile selection is set to "R" on
the instrument. The tracing stylus moves automatically across the
sample surface. The length of each trace (L.sub.T) is 17.5
millimeter composed of 7 sequential sample lengths L.sub.C of 2.5
mm. The measuring length (L.sub.m) is 12.5 millimeter and is
composed of the 5 sequential sample lengths (L.sub.C) obtained by
eliminating the first and the last sections of each trace. The
average value of individual roughness depths in these five
sequential sample lengths L.sub.C is determined and R.sub.Z is the
average of ten such determinations, five taken in the machine
direction of extrusion (MD) and five in the cross machine direction
(CMD). The distance between two consecutive traces in each
direction is 3 mm. R.sub.SM, the average peak distance, is
determined from the same measurement as for R.sub.Z. Mean distance
of all profile peaks within the each measuring length (L.sub.m) is
determined and the reported R.sub.SM for each machine direction is
the average of five such determinations on that direction. Set-up
switch positions on the Perthometer during R.sub.Z and R.sub.SM are
as follows: Filter: GS, Profile: R, LC: N 2.5 mm, LT: 17.5 mm, VB:
625 micrometers. R.sub.Z and R.sub.SM values herein throughout are
given in micrometers.
Polymer layers of the present invention are also characterized by
their "permanence," which is determined according to the following
technique: For polymer layers that are embossed, a polymer layer is
measured for R.sub.Z (R.sub.Z Base) prior to embossing. After
embossing, a second R.sub.Z measurement is taken (R.sub.Z Final).
For polymer layers that are not embossed a roughness measurement,
R.sub.Z, is taken and designated R.sub.Z Final, and R.sub.Z Base is
given the value zero. For both embossed and non-embossed layers, a
12.7 centimeter square sample is then cut from the polymer layer.
Poly(ethylene terephthalate) film is placed on the edges of one
half of a wood frame resting on a horizontal surface, wherein the
frame periphery is slightly smaller than the polymer layer sample.
The polymer layer sample is then placed on the wood frame so that
the poly(ethylene terephthalate) film is between the wood frame and
the edges of the polymer layer, in which position it prevents the
polymer film from adhering to the wood frame, which would make
disassembly difficult. A second poly(ethylene terephthalate) film
is then place over the polymer layer, and the second half of the
wooden frame is then placed on top of the poly(ethylene
terephthalate) film. The two frame halves are then clamped together
with binder clips, thereby sandwiching the polymer layer between
the two poly(ethylene terephthalate) films and the two frame
halves. The frame and polymer assembly is then placed in a
preheated oven for 5 minutes at 100.degree. C. The assembly is then
removed and allowed to cool. Another R.sub.Z value is then
determined for the polymer layer sample (R.sub.Z 100.degree.
C.).
A permanence value can then be determined according to the
following formula:
.times..times..times..degree..times..times..times..times..times..times..t-
imes..times..times. ##EQU00002##
The following procedure is used to measure mottle: A shadow graph
light (a xenon light powered by a kni-tron rectifier (model number
R-2120-2) from Kneisley Electric company, Toledo, Ohio) is
positioned in a dark room at 1 meter from a white surface. A sample
is held between the white surface and the light source next to a
"maximum standard level" standard laminate that represents the
lowest acceptable optical quality. The image projected on the white
surface is visually examined. If the sample image is worse than the
maximum standard level standard, then the sample is rejected as
having too much distortion. If the sample is at least as good as
the maximum standard level standard, then the sample is compared to
progressively optically superior standards until a grade is
determined for the sample. The sample is evaluated in the cross
machine direction and the machine direction, and the worst grade of
the two is designated the grade for the sample. A grade of 0
indicates that no optical distortion is visible. A grade of 1 or 2
indicates some minor distortion is observable. A grade of 3 to 4
indicates that more than minor distortion is apparent. A grade of 5
or higher indicates that significant distortion is observable and
the laminate would likely be unusable in applications that require
visual clarity, such as in automobile windshields.
The clarity of a polymer layer, and particularly a poly(vinyl
butyral) layer, can be determined by measuring the haze value,
which is a quantification of the amount of light scattered away
from the direction of the incident beam in passing through the
layer. The percent haze can be measured according to the following
technique. An apparatus for measuring the amount of haze, a
Hazemeter, Model D25, which is available from Hunter Associates
(Reston, Va.), can be used in accordance with ASTM D1003-61
(Re-approved 1977)-Procedure A, using Illuminant C, at an observer
angle of 2 degrees. In various embodiments of the present
invention, percent haze is less than 5%, less than 3%, and less
than 1%.
The visible transmittance can be quantified using a UV-Vis-NIR
spectrophotometer such as the Lambda 900 made by Perkin Elmer Corp.
by methods described in international standard ISO 9050:1990. In
various embodiments, the transmittance through a polymer layer of
the present invention is at least 60%, at least 70%, or at least
80%.
Pummel adhesion can be measured according to the following
technique, and where "pummel" is referred to herein to quantify
adhesion of a polymer layer to glass, the following technique is
used to determine pummel. Two-ply glass laminate samples are
prepared with standard autoclave lamination conditions. The
laminates are cooled to about -18.degree. C. (0.degree. F.) and
manually pummeled with a hammer to break the glass. All broken
glass that is not adhered to the poly(vinyl butyral) layer is then
removed, and the amount of glass left adhered to the poly(vinyl
butyral) layer is visually compared with a set of standards. The
standards correspond to a scale in which varying degrees of glass
remain adhered to the poly(vinyl butyral) layer. In particular, at
a pummel standard of zero, no glass is left adhered to the
poly(vinyl butyral) layer. At a pummel standard of 10, 100% of the
glass remains adhered to the poly(vinyl butyral) layer. Poly(vinyl
butyral) layers of the present invention can have, for example, a
pummel value of between 3 and 10.
Tensile break stress can be determined for a polymer layer
according to the procedure described in JIS K6771.
EXAMPLES
Example 1
Two, three-layer interlayer samples are separately coextruded in a
length that can be later cut into three separate interlayers. Each
interlayer comprises a 0.1524 millimeter (6 mil) layer sandwiched
between two 0.3302 millimeters (13 mil) layers for a total
thickness of 0.8128 millimeters (32 mils). The inner layer
comprises 75 phr plasticizer (triethylene glycol
di-(2-ethylhexanoate)) and 11.0% residual polyvinyl alcohol, while
the outside layers comprise 38 phr plasticizer (triethylene glycol
di-(2-ethylhexanoate)) and 18.5% residual polyvinyl alcohol.
Surface characteristics of the two interlayer samples are
controlled during coextrusion with melt fracture to provide
differing levels of R.sub.Z. The first interlayer--sample A--has an
R.sub.Z of about 20. The second interlayer--sample B--has an
R.sub.Z of about 40. The exact R.sub.Z values are given in Table 1,
where "CMD" is cross machine direction and "MD" is machine
direction and where measurements from both sides of each interlayer
are shown:
TABLE-US-00001 TABLE 1 CMD MD Sample R.sub.Z R.sub.SM R.sub.Z
R.sub.SM A (Side 1) 21.4 256.5 21.7 407.2 A (Side 2) 22.6 277.5
21.4 368.4 B (Side 1) 42.5 405.9 40.2 619.2 B (Side 2) 40.6 396.3
41.8 635.0
Sample A is then cut into four separate interlayers and sample B is
also divided into four separate interlayers.
Three of the separate interlayers for each sample is then embossed.
Embossing is performed as described elsewhere herein with an
embossing pattern of 49.2 lines per centimeter (125 lines per
inch). One interlayer of each sample is left unembossed.
The Tables below provide the embossing conditions and the resulting
R.sub.SM and R.sub.Z.
Table 2 shows the results for interlayers formed from sample A and
from sample B that are embossed at 174.degree. C. (345.degree. F.)
at a rate of 7.6 meters (25 feet) per minute.
TABLE-US-00002 TABLE 2 CMD MD Sample R.sub.Z R.sub.SM R.sub.Z
R.sub.SM A (Side 1) 31.3 287.0 34.3 266.1 A (Side 2) 33.9 281.7
35.6 298.1 B (Side 1) 51.2 300.0 53.0 335.2 B (Side 2) 54.2 319.8
52.5 375.7
Table 3 shows the results for interlayers formed from sample A and
from sample B that are embossed at 193.degree. C. (380.degree. F.)
at a rate of 7.6 meters (25 feet) per minute.
TABLE-US-00003 TABLE 3 CMD MD Sample R.sub.Z R.sub.SM R.sub.Z
R.sub.SM A (Side 1) 39.3 286.7 41.3 292.1 A (Side 2) 43.1 280.4
42.9 285.5 B (Side 1) 55.5 310.0 57.5 348.3 B (Side 2) 56.5 312.7
55.1 312.9
Table 4 shows the results for interlayers formed from sample A and
from sample B that are embossed at 204.degree. C. (400.degree. F.)
at a rate of 4.6 meters (15 feet) per minute.
TABLE-US-00004 TABLE 4 CMD MD Sample R.sub.Z R.sub.SM R.sub.Z
R.sub.SM A (Side 1) 59.0 280.3 59.8 282.8 A (Side 2) 61.0 297.6
61.8 266.0 B (Side 1) 69.4 266.0 71.7 290.7 B (Side 2) 67.6 311.5
67.8 279.3
The six embossed samples shown in Tables 2, 3, and 4 are then
placed in a frame and polymer assembly, according to the method for
testing permanence as described in detail, above, and the frame and
polymer assembly are then placed in a preheated oven for 5 minutes
at 100.degree. C. After cooling the six embossed samples are tested
again for R.sub.SM and R.sub.Z, and the results are show in Tables
5, 6, and 7.
Table 5 shows the results for interlayers formed from sample A and
from sample B that are embossed at 174.degree. C. (345.degree. F.)
at a rate of 7.6 meters (25 feet) per minute.
TABLE-US-00005 TABLE 5 CMD MD Sample R.sub.Z R.sub.SM R.sub.Z
R.sub.SM A (Side 1) 25.6 293.7 26.8 323.4 A (Side 2) 25.7 276.0
24.9 332.7 B (Side 1) 49.1 387.7 51.2 571.8 B (Side 2) 55.1 478.1
52.8 620.6
Table 6 shows the results for interlayers formed from sample A and
from sample B that are embossed at 193.degree. C. (380.degree. F.)
at a rate of 7.6 meters (25 feet) per minute.
TABLE-US-00006 TABLE 6 CMD MD Sample R.sub.Z R.sub.SM R.sub.Z
R.sub.SM A (Side 1) 28.7 281.8 30.2 300.5 A (Side 2) 30.2 273.3
31.3 293.6 B (Side 1) 50.8 374.3 55.1 450.3 B (Side 2) 51.0 370.3
52.6 429.4
Table 7 shows the results for interlayers formed from sample A and
from sample B that are embossed at 204.degree. C. (400.degree. F.)
at a rate of 4.6 meters (15 feet) per minute.
TABLE-US-00007 TABLE 7 CMD MD Sample R.sub.Z R.sub.SM R.sub.Z
R.sub.SM A (Side 1) 47.4 277.8 49.0 292.1 A (Side 2) 50.4 294.9
50.7 269.5 B (Side 1) 60.9 284.3 65.8 305.9 B (Side 2) 60.9 330.8
64.6 295.1
From the data in Tables 1 through 7, permanence values for each of
the six embossed interlayers are determined, according to the
method provided elsewhere herein. Results are provided in Table
8.
TABLE-US-00008 TABLE 8 174.degree. C. at 193.degree. C. at
204.degree. C. at 7.6 meters per 7.6 meters per 4.6 meters per
minute minute minute Sample Permanence Sample Permanence Sample
Permanence A 52.0 A 67.1 A (Side 1) 89.0 (Side 1) (Side 1) A 41.8 A
67.4 A (Side 2) 90.2 (Side 2) (Side 2) B 44.9 B 70.2 B (Side 1)
91.6 (Side 1) (Side 1) B 38.9 B 69.4 B (Side 2) 92.3 (Side 2) (Side
2)
The six embossed samples, as well as the two samples that are
unembossed, are placed between two panes of glass and laminated.
Lamination is a multistep process in which the poly(vinyl butyral)
sheets and glass are converted to a combined final form of safety
glass having desirable performance and optical clarity
characteristics.
Vacuum bag deairing is a technique that is used to evacuate air
from a rigid substrate/interlayer/rigid substrate construction
prior to the final step of autoclaving. It frequently can be
employed to improve autoclave yields in commercial operations.
Samples are placed in a resilient rubber bag, which is then
evacuated by a vacuum hose mated to the bag. In one embodiment, the
bag is brought up to and held at a temperature of about 50.degree.
C. for 60 minutes and then to 120.degree. C. for 20 minutes while
under vacuum. The bag is then cooled and the resulting panel is
removed and placed in an autoclave for final finishing.
Light transmission measurements, as a percentage, are taken after
vacuum bag deairing and before autoclaving. A higher number
indicates low cloudiness, which means that little or no air remains
in the rigid substrate/interlayer/rigid substrate construct.
Mottle measurements are taken after autoclaving.
Light transmission is tested with an adhesion photometer (Tokyo
Denshoku #S-904356). Each laminate is tested eight times at
dispersed locations throughout the laminate, and the eight results
are averaged to give light transmission, as shown in Table 9, where
LT is light transmission.
TABLE-US-00009 TABLE 9 174.degree. C. at 7.6 193.degree. C. at 7.6
204.degree. C. at 4.6 meters per meters per meters per Unembossed
minute minute minute Sample LT Sample LT Sample LT Sample LT A 63.4
A 99.4 A 99.6 A 99.4 B 67.8 B 99.0 B 99.5 B 99.4
Mottle is determined as described elsewhere herein, with results
from 5 observers averaged to provide a final mottle grade. Results
are shown in Table 10, where "Smp" is sample, "MD" is machine
direction, "CMD" is cross machine direction, and "Final" is the
mottle grade, which is the greater of the machine direction and
cross machine direction results.
TABLE-US-00010 TABLE 10 174.degree. C. at 7.6 193.degree. C. at 7.6
204.degree. C. at 4.6 Unembossed meters per minute meters per
minute meters per minute Mottle Mottle Mottle Mottle (MD/ (MD/ (MD/
(MD/ Smp CMD/Final) Smp CMD/Final) Smp CMD/Ave) Smp CMD/Final) A
1/1/1 A 1/1/1 A 1/1/1 A 1/1/1 B 3.0/3.8/3.8 B 3.4/3.4/3.4 B
2.8/2.8/2.8 B 2.8/2.8/2.8
By virtue of the present invention, it is now possible to provide
multiple layer interlayers that reduce sound transmission and that
are easily handled and readily incorporated into multiple layer
constructs, such as laminated glass panels for windshields and
architectural windows.
While the invention has been described with reference to exemplary
embodiments, it will be understood by those skilled in the art that
various changes may be made and equivalents may be substituted for
elements thereof without departing from the scope of the invention.
In addition, many modifications may be made to adapt a particular
situation or material to the teachings of the invention without
departing from the essential scope thereof. Therefore, it is
intended that the invention not be limited to the particular
embodiments disclosed as the best mode contemplated for carrying
out this invention, but that the invention will include all
embodiments falling within the scope of the appended claims.
It will further be understood that any of the ranges, values, or
characteristics given for any single component of the present
invention can be used interchangeably with any ranges, values, or
characteristics given for any of the other components of the
invention, where compatible, to form an embodiment having defined
values for each of the components, as given herein throughout. For
example, a polymer layer can be formed comprising residual acetate
content in any of the ranges given in addition to any of the ranges
given for plasticizer, as well as having any of the R.sub.Z,
R.sub.SM, and permanence values given, where appropriate, to form
many permutations that are within the scope of the present
invention but that would be cumbersome to list.
Any figure reference numbers given within the abstract or any
claims are for illustrative purposes only and should not be
construed to limit the claimed invention to any one particular
embodiment shown in any FIGURE.
Figures are not drawn to scale unless otherwise indicated.
Each reference, including journal articles, patents, applications,
and books, referred to herein is hereby incorporated by reference
in its entirety.
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